/*
 * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.swing.plaf;

import javax.swing.JComponent;
import javax.swing.SwingUtilities;
import javax.accessibility.Accessible;

import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Insets;


/**
 * The base class for all UI delegate objects in the Swing pluggable
 * look and feel architecture.  The UI delegate object for a Swing
 * component is responsible for implementing the aspects of the
 * component that depend on the look and feel.
 * The <code>JComponent</code> class
 * invokes methods from this class in order to delegate operations
 * (painting, layout calculations, etc.) that may vary depending on the
 * look and feel installed.  <b>Client programs should not invoke methods
 * on this class directly.</b>
 *
 * @see javax.swing.JComponent
 * @see javax.swing.UIManager
 */
public abstract class ComponentUI {

  /**
   * Sole constructor. (For invocation by subclass constructors,
   * typically implicit.)
   */
  public ComponentUI() {
  }

  /**
   * Configures the specified component appropriately for the look and feel.
   * This method is invoked when the <code>ComponentUI</code> instance is being installed
   * as the UI delegate on the specified component.  This method should
   * completely configure the component for the look and feel,
   * including the following:
   * <ol>
   * <li>Install default property values for color, fonts, borders,
   * icons, opacity, etc. on the component.  Whenever possible,
   * property values initialized by the client program should <i>not</i>
   * be overridden.
   * <li>Install a <code>LayoutManager</code> on the component if necessary.
   * <li>Create/add any required sub-components to the component.
   * <li>Create/install event listeners on the component.
   * <li>Create/install a <code>PropertyChangeListener</code> on the component in order
   * to detect and respond to component property changes appropriately.
   * <li>Install keyboard UI (mnemonics, traversal, etc.) on the component.
   * <li>Initialize any appropriate instance data.
   * </ol>
   *
   * @param c the component where this UI delegate is being installed
   * @see #uninstallUI
   * @see javax.swing.JComponent#setUI
   * @see javax.swing.JComponent#updateUI
   */
  public void installUI(JComponent c) {
  }

  /**
   * Reverses configuration which was done on the specified component during
   * <code>installUI</code>.  This method is invoked when this
   * <code>UIComponent</code> instance is being removed as the UI delegate
   * for the specified component.  This method should undo the
   * configuration performed in <code>installUI</code>, being careful to
   * leave the <code>JComponent</code> instance in a clean state (no
   * extraneous listeners, look-and-feel-specific property objects, etc.).
   * This should include the following:
   * <ol>
   * <li>Remove any UI-set borders from the component.
   * <li>Remove any UI-set layout managers on the component.
   * <li>Remove any UI-added sub-components from the component.
   * <li>Remove any UI-added event/property listeners from the component.
   * <li>Remove any UI-installed keyboard UI from the component.
   * <li>Nullify any allocated instance data objects to allow for GC.
   * </ol>
   *
   * @param c the component from which this UI delegate is being removed; this argument is often
   * ignored, but might be used if the UI object is stateless and shared by multiple components
   * @see #installUI
   * @see javax.swing.JComponent#updateUI
   */
  public void uninstallUI(JComponent c) {
  }

  /**
   * Paints the specified component appropriately for the look and feel.
   * This method is invoked from the <code>ComponentUI.update</code> method when
   * the specified component is being painted.  Subclasses should override
   * this method and use the specified <code>Graphics</code> object to
   * render the content of the component.
   *
   * @param g the <code>Graphics</code> context in which to paint
   * @param c the component being painted; this argument is often ignored, but might be used if the
   * UI object is stateless and shared by multiple components
   * @see #update
   */
  public void paint(Graphics g, JComponent c) {
  }

  /**
   * Notifies this UI delegate that it is time to paint the specified
   * component.  This method is invoked by <code>JComponent</code>
   * when the specified component is being painted.
   *
   * <p>By default this method fills the specified component with
   * its background color if its {@code opaque} property is {@code true},
   * and then immediately calls {@code paint}. In general this method need
   * not be overridden by subclasses; all look-and-feel rendering code should
   * reside in the {@code paint} method.
   *
   * @param g the <code>Graphics</code> context in which to paint
   * @param c the component being painted; this argument is often ignored, but might be used if the
   * UI object is stateless and shared by multiple components
   * @see #paint
   * @see javax.swing.JComponent#paintComponent
   */
  public void update(Graphics g, JComponent c) {
    if (c.isOpaque()) {
      g.setColor(c.getBackground());
      g.fillRect(0, 0, c.getWidth(), c.getHeight());
    }
    paint(g, c);
  }

  /**
   * Returns the specified component's preferred size appropriate for
   * the look and feel.  If <code>null</code> is returned, the preferred
   * size will be calculated by the component's layout manager instead
   * (this is the preferred approach for any component with a specific
   * layout manager installed).  The default implementation of this
   * method returns <code>null</code>.
   *
   * @param c the component whose preferred size is being queried; this argument is often ignored,
   * but might be used if the UI object is stateless and shared by multiple components
   * @see javax.swing.JComponent#getPreferredSize
   * @see java.awt.LayoutManager#preferredLayoutSize
   */
  public Dimension getPreferredSize(JComponent c) {
    return null;
  }

  /**
   * Returns the specified component's minimum size appropriate for
   * the look and feel.  If <code>null</code> is returned, the minimum
   * size will be calculated by the component's layout manager instead
   * (this is the preferred approach for any component with a specific
   * layout manager installed).  The default implementation of this
   * method invokes <code>getPreferredSize</code> and returns that value.
   *
   * @param c the component whose minimum size is being queried; this argument is often ignored, but
   * might be used if the UI object is stateless and shared by multiple components
   * @return a <code>Dimension</code> object or <code>null</code>
   * @see javax.swing.JComponent#getMinimumSize
   * @see java.awt.LayoutManager#minimumLayoutSize
   * @see #getPreferredSize
   */
  public Dimension getMinimumSize(JComponent c) {
    return getPreferredSize(c);
  }

  /**
   * Returns the specified component's maximum size appropriate for
   * the look and feel.  If <code>null</code> is returned, the maximum
   * size will be calculated by the component's layout manager instead
   * (this is the preferred approach for any component with a specific
   * layout manager installed).  The default implementation of this
   * method invokes <code>getPreferredSize</code> and returns that value.
   *
   * @param c the component whose maximum size is being queried; this argument is often ignored, but
   * might be used if the UI object is stateless and shared by multiple components
   * @return a <code>Dimension</code> object or <code>null</code>
   * @see javax.swing.JComponent#getMaximumSize
   * @see java.awt.LayoutManager2#maximumLayoutSize
   */
  public Dimension getMaximumSize(JComponent c) {
    return getPreferredSize(c);
  }

  /**
   * Returns <code>true</code> if the specified <i>x,y</i> location is
   * contained within the look and feel's defined shape of the specified
   * component. <code>x</code> and <code>y</code> are defined to be relative
   * to the coordinate system of the specified component.  Although
   * a component's <code>bounds</code> is constrained to a rectangle,
   * this method provides the means for defining a non-rectangular
   * shape within those bounds for the purpose of hit detection.
   *
   * @param c the component where the <i>x,y</i> location is being queried; this argument is often
   * ignored, but might be used if the UI object is stateless and shared by multiple components
   * @param x the <i>x</i> coordinate of the point
   * @param y the <i>y</i> coordinate of the point
   * @see javax.swing.JComponent#contains
   * @see java.awt.Component#contains
   */
  @SuppressWarnings("deprecation")
  public boolean contains(JComponent c, int x, int y) {
    return c.inside(x, y);
  }

  /**
   * Returns an instance of the UI delegate for the specified component.
   * Each subclass must provide its own static <code>createUI</code>
   * method that returns an instance of that UI delegate subclass.
   * If the UI delegate subclass is stateless, it may return an instance
   * that is shared by multiple components.  If the UI delegate is
   * stateful, then it should return a new instance per component.
   * The default implementation of this method throws an error, as it
   * should never be invoked.
   */
  public static ComponentUI createUI(JComponent c) {
    throw new Error("ComponentUI.createUI not implemented.");
  }

  /**
   * Returns the baseline.  The baseline is measured from the top of
   * the component.  This method is primarily meant for
   * <code>LayoutManager</code>s to align components along their
   * baseline.  A return value less than 0 indicates this component
   * does not have a reasonable baseline and that
   * <code>LayoutManager</code>s should not align this component on
   * its baseline.
   * <p>
   * This method returns -1.  Subclasses that have a meaningful baseline
   * should override appropriately.
   *
   * @param c <code>JComponent</code> baseline is being requested for
   * @param width the width to get the baseline for
   * @param height the height to get the baseline for
   * @return baseline or a value &lt; 0 indicating there is no reasonable baseline
   * @throws NullPointerException if <code>c</code> is <code>null</code>
   * @throws IllegalArgumentException if width or height is &lt; 0
   * @see javax.swing.JComponent#getBaseline(int, int)
   * @since 1.6
   */
  public int getBaseline(JComponent c, int width, int height) {
    if (c == null) {
      throw new NullPointerException("Component must be non-null");
    }
    if (width < 0 || height < 0) {
      throw new IllegalArgumentException(
          "Width and height must be >= 0");
    }
    return -1;
  }

  /**
   * Returns an enum indicating how the baseline of he component
   * changes as the size changes.  This method is primarily meant for
   * layout managers and GUI builders.
   * <p>
   * This method returns <code>BaselineResizeBehavior.OTHER</code>.
   * Subclasses that support a baseline should override appropriately.
   *
   * @param c <code>JComponent</code> to return baseline resize behavior for
   * @return an enum indicating how the baseline changes as the component size changes
   * @throws NullPointerException if <code>c</code> is <code>null</code>
   * @see javax.swing.JComponent#getBaseline(int, int)
   * @since 1.6
   */
  public Component.BaselineResizeBehavior getBaselineResizeBehavior(
      JComponent c) {
    if (c == null) {
      throw new NullPointerException("Component must be non-null");
    }
    return Component.BaselineResizeBehavior.OTHER;
  }

  /**
   * Returns the number of accessible children in the object.  If all
   * of the children of this object implement <code>Accessible</code>,
   * this
   * method should return the number of children of this object.
   * UIs might wish to override this if they present areas on the
   * screen that can be viewed as components, but actual components
   * are not used for presenting those areas.
   *
   * Note: As of v1.3, it is recommended that developers call
   * <code>Component.AccessibleAWTComponent.getAccessibleChildrenCount()</code> instead
   * of this method.
   *
   * @return the number of accessible children in the object
   * @see #getAccessibleChild
   */
  public int getAccessibleChildrenCount(JComponent c) {
    return SwingUtilities.getAccessibleChildrenCount(c);
  }

  /**
   * Returns the <code>i</code>th <code>Accessible</code> child of the object.
   * UIs might need to override this if they present areas on the
   * screen that can be viewed as components, but actual components
   * are not used for presenting those areas.
   *
   * <p>
   *
   * Note: As of v1.3, it is recommended that developers call
   * <code>Component.AccessibleAWTComponent.getAccessibleChild()</code> instead of
   * this method.
   *
   * @param i zero-based index of child
   * @return the <code>i</code>th <code>Accessible</code> child of the object
   * @see #getAccessibleChildrenCount
   */
  public Accessible getAccessibleChild(JComponent c, int i) {
    return SwingUtilities.getAccessibleChild(c, i);
  }
}
